President Trump is planning an announcement tomorrow that could send shock waves through the Middle East. He is planning to declare that the capital of Israel is Jerusalem, and he's asking the State Department to start work on moving the U.S. embassy from Tel Aviv to Jerusalem. That won't happen right away, but the signals he is sending now could well spark protests across the region. NPR's Michele Kelemen joins us now from the State Department to talk about this. Hey, Michele.

MICHELE KELEMEN, BYLINE: Hi, Mary Louise.

KELLY: Why is President Trump announcing this move now?

KELEMEN: Well, his aides say that it's a recognition of reality. Jerusalem is where the Israeli government is. And Trump promised to do this during the campaign. Besides, they argue that putting off the move as previous administrations have done haven't helped Israelis and Palestinians get anywhere closer to peace.

KELLY: Now, I mentioned this could spark protests around the region. It already has sparked diplomatic protests from across the Arab world. Why is this so controversial?

KELEMEN: Well, because Palestinians claim East Jerusalem as the capital of their future state. Israel captured that part of the city in the 1967 war. And it's always been seen as what's called the final status issue - one of the final status issues, something that has to be decided in peace talks. Administration officials say that will still be the case. But as you mentioned, we're hearing lots of concern from the region. The Jordanians, the Saudis and others have been warning that this could raise tensions. Palestinians, too, are promising protests or what they're calling days of rage.

KELLY: Is the State Department preparing for that, beefing up security at embassies?

KELEMEN: Yeah, it's beefing up security at embassies. It's also warning embassy employees and their families to stay away from Jerusalem's Old City as well as Bethlehem, Jericho and other parts of the West Bank. And it's warning Americans who are in Israel to stay away from crowds. We're also expecting those kinds of warnings to go out in other capitals in the region.

KELLY: This is something that has been talked about in Washington for a long time. Congress passed a law back in the '90s to move the embassy. How quickly could it move?

KELEMEN: Well, administration officials say it's going to take time. They're even talking about years. They say they can't just change the plaque on the U.S. consulate in Jerusalem, that they're going to have to find a new site and build it, get money from Congress. And in the meantime, President Trump is expected to sign another waiver of that law as previous presidents have done.

KELLY: And I guess the big question hanging over this is what might this do to prospects for peace.

KELEMEN: Well, Palestinians and their supporters could walk away, but the Trump administration doesn't sound too worried about that. The administration seems to be counting on Arab leaders to keep this from spiraling out of control, and that's a really big gamble. I have to say, you know, if violence starts, if their people get killed, it's really hard to get peace talks going.